Method for establishing layer-2 entities for d2d communication system and device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for establishing layer-2 entities for D2D communication system, the method comprising: configuring a sidelink radio bearer over which the UE transmits data to a peer UE; establishing RLC (Radio Link Control) and PDCP (Packet Data Convergence Protocol) entities for the sidelink radio bearer by selecting one of configuration information sets, wherein each configuration information set is identified by each configuration information index; and transmitting configuration information of the sidelink radio bearer via a sidelink to the peer UE, wherein the UE is directly connected to the peer UE via the sidelink.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method establishing layer-2 entities for D2D(Device to Device) communication system and a device therefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Device to device (D2D) communication refers to the distributedcommunication technology that directly transfers traffic betweenadjacent nodes without using infrastructure such as a base station. In aD2D communication environment, each node such as a portable terminaldiscovers user equipment physically adjacent thereto and transmitstraffic after setting communication session. In this way, since D2Dcommunication may solve traffic overload by distributing trafficconcentrated into the base station, the D2D communication may havereceived attention as the element technology of the next generationmobile communication technology after 4G. For this reason, the standardinstitute such as 3GPP or IEEE has proceeded to establish the D2Dcommunication standard on the basis of LTE-A or Wi-Fi, and Qualcomm hasdeveloped their own D2D communication technology.

It is expected that the D2D communication contributes to increasethroughput of a mobile communication system and create new communicationservices. Also, the D2D communication may support proximity based socialnetwork services or network game services. The problem of link of a userequipment located at a shade zone may be solved by using a D2D link as arelay. In this way, it is expected that the D2D technology will providenew services in various fields.

The D2D communication technologies such as infrared communication,ZigBee, radio frequency identification (RFID) and near fieldcommunications (NFC) based on the RFID have been already used. However,since these technologies support communication only of a specific objectwithin a limited distance (about 1 m), it is difficult for thetechnologies to be regarded as the D2D communication technologiesstrictly.

Although the D2D communication has been described as above, details of amethod for transmitting data from a plurality of D2D user equipmentswith the same resource have not been suggested.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method and device for establisinglayer-2 entities (e.g. RLC entity orPDCP entity) for D2D communication system. The technical problems solvedby the present invention are not limited to the above technical problemsand those skilled in the art may understand other technical problemsfrom the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for a User Equipment (UE) operating in a wireless communicationsystem, the method comprising: configuring a sidelink radio bearer overwhich the UE transmits data to a peer UE; establishing RLC (Radio LinkControl) and PDCP (Packet Data Convergence Protocol) entities for thesidelink radio bearer by selecting one of configuration informationsets, wherein each configuration information set is identified by eachconfiguration information index; and transmitting an index of theselected configuration information set via a sidelink to the peer UE,wherein the UE is directly connected to the peer UE via the sidelink.

Preferably, the method further comprises: configuring, by the UE,mapping relation between configuration information sets and indices; andtransmitting the mapping relation to the peer UE.

Preferably, the method further comprises: receiving, by the UE, mappingrelation between configuration information sets and indices from anetwork

Preferably, wherein LCID is used for the configuration informationindex, wherein the LCID is an identifier of a logical channel of thesidelink radio bearer.

Preferably, the index of the selected configuration information set istransmitted one or multiple times to the peer UE, wherein a transmissionnumber of the index is configured by the network or pre-defined.

Preferably, the index of the selected configuration information set istransmitted periodically to the peer UE, wherein periodicity oftransmitting the index is configured by the network or pre-defined.

Preferably, the index of the selected configuration information set istransmitted as form of at least one of RRC (Radio Resource Control),PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC(Medium Access Control), or PHY (PHYsical layer) signal.

Preferably, the index of the selected configuration information set istransmitted via a first D2D (Device to Device) packet, wherein the firstD2D packet is transmitted before transmitting any other D2D packets ofthe sidelink radio bearer to the peer UE.

Preferably, the first D2D packet further includes at least one of atarget ID, a source ID or a LCID.

In another aspect of the present invention, provided herein is a methodfor a User Equipment (UE) operating in a wireless communication system,the method comprising: receiving an index of a configuration informationset via a sidelink from the peer UE, wherein the UE is directlyconnected to the peer UE via the sidelink and, wherein the configurationinformation set corresponds to a sidelink radio bearer to be configured;configuring the sidelink radio bearer according to the configurationinformation set indicated by the index; and establishing RLC (Radio LinkControl) and PDCP (Packet Data Convergence Protocol) entities for thesidelink radio bearer if the RLC and PDCP entities are not establishedyet.

Preferably, the method further comprises: receiving, by the UE, mappingrelation between configuration information sets and indices from thepeer UE or a network.

Preferably, LCID is used for the configuration information index,wherein the LCID is an identifier of a logical channel of the sidelinkradio bearer. And one or more LCIDs are associated with oneconfiguration information set.

Preferably, each configuration information set includes at least one ofparameters including a PDCP-SN-Size, a headerCompression, aSN-FieldLength and a T-Reordering.

Preferably, the index of the configuration information set is receivedvia a first D2D (Device to Device) packet, wherein the first D2D packetis received before receiving any other D2D packets of the sidelink radiobearer from the peer UE.

Preferably, the first D2D packet further includes at least one of atarget ID, a source ID or a LCID.

Preferably, the method further comprises: delivering wherein the indexof the configuration information set to the established RLC and PDCPentities.

Preferably, the method further comprises: ignoring the received theindex of the configuration information set if the RLC and PDCP entitiesare already established.

Preferably, the method further comprises: updating the RLC and PDCPentities for the sidelink associated with a targetID, a sourceID, and aLCID by setting the PDCP-SN-Size, the headerCompression, theSN-FieldLength, and the T-Reordering to the values in the configurationinformation set indicated by the index.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, an RLC entity and a PDCP entity canbe efficiently established in D2D communication system. It will beappreciated by persons skilled in the art that that the effects achievedby the present invention are not limited to what has been particularlydescribed hereinabove and other advantages of the present invention willbe more clearly understood from the following detailed description takenin conjunction with the accompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention;

FIG. 6 is an example of default data path for a normal communication;

FIGS. 7-8 are examples of data path scenarios for a proximitycommunication;

FIG. 9 is a conceptual diagram illustrating for a non-roaming referencearchitecture;

FIG. 10 is a conceptual diagram illustrating for a Layer 2 Structure forSidelink;

FIG. 11a is a conceptual diagram illustrating for User-Plane protocolstack for ProSe Direct Communication, and FIG. 11b is Control-Planeprotocol stack for ProSe Direct Communication;

FIG. 12 is a conceptual diagram illustrating for a PC5 interface forProSe Direct Discovery;

FIG. 13 is a conceptual diagram illustrating for overview model of theRLC sub layer;

FIG. 14 is a conceptual diagram illustrating for model of twounacknowledged mode peer entities;

FIG. 15 is a conceptual diagram for functional view of a PDCP entity;

FIG. 16 is a conceptual diagram for transmitting aRadioResourceConfigDedicated from E-UTRAN to a UE; and

FIGS. 17-19 are conceptual diagrams for establishing layer-2 entitiesfor D2D communication according to embodiments of the present invention.

BEST MODE

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTEIDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certam subframe.Then, one or more UEs located in a cell monitor the PDCCH using its RNTIinformation. And, a specific UE with RNTI “A” reads the PDCCH and thenreceive the PDSCH indicated by B and C in the PDCCH information.

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transciver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

Recently, Proximity-based Service (ProSe) has been discussed in 3GPP.The ProSe enables different UEs to be connected (directly) each other(after appropriate procedure(s), such as authentication), through eNBonly (but not further through Serving Gateway (SGW)/Packet Data NetworkGateway (PDN-GW, PGW)), or through SGW/PGW. Thus, using the ProSe,device to device direct communication can be provided, and it isexpected that every devices will be connected with ubiquitousconnectivity. Direct communication between devices in a near distancecan lessen the load of network. Recently, proximity-based social networkservices have come to public attention, and new kinds of proximity-basedapplications can be emerged and may create new business market andrevenue. For the first step, public safety and critical communicationare required in the market. Group communication is also one of keycomponents in the public safety system. Required functionalities are:Discovery based on proximity, Direct path communication, and Managementof group communications.

Use cases and scenarios are for example: i) Commercial/social use, ii)Network offloading, iii) Public Safety, iv) Integration of currentinfrastructure services, to assure the consistency of the userexperience including reachability and mobility aspects, and v) PublicSafety, in case of absence of EUTRAN coverage (subject to regionalregulation and operator policy, and limited to specific public-safetydesignated frequency bands and terminals)

FIG. 6 is an example of default data path for communication between twoUEs. With reference to FIG. 6, even when two UEs (e.g., UE1, UE2) inclose proximity communicate with each other, their data path (userplane) goes via the operator network. Thus a typical data path for thecommunication involves eNB(s) and/or Gateway(s) (GW(s)) (e.g., SGW/PGW).

FIGS. 7 and 8 are examples of data path scenarios for a proximitycommunication. If wireless devices (e.g., UE1, UE2) are in proximity ofeach other, they may be able to use a direct mode data path (FIG. 7) ora locally routed data path (FIG. 8). In the direct mode data path,wireless devices are connected directly each other (after appropriateprocedure(s), such as authentication), without eNB and SGW/PGW. In thelocally routed data path, wireless devices are connected each otherthrough eNB only.

FIG. 9 is a conceptual diagram illustrating for a non-roaming referencearchitecture.

PC1 to PC 5 represent interfaces. PC1 is a reference point between aProSe application in a UE and a ProSe App server. It is used to defineapplication level signaling requirements. PC 2 is a reference pointbetween the ProSe App Server and the ProSe Function. It is used todefine the interaction between ProSe App Server and ProSe functionalityprovided by the 3GPP EPS via ProSe Function. One example may be forapplication data updates for a ProSe database in the ProSe Function.Another example may be data for use by ProSe App Server in interworkingbetween 3GPP functionality and application data, e.g. name translation.PC3 is a reference point between the UE and ProSe Function. It is usedto define the interaction between UE and ProSe Function. An example maybe to use for configuration for ProSe discovery and communication. PC4is a reference point between the EPC and ProSe Function. It is used todefine the interaction between EPC and ProSe Function. Possible usecases may be when setting up a one-to-one communication path between UEsor when validating ProSe services (authorization) for session managementor mobility management in real time.

PC5 is a reference point between UE to UE used for control and userplane for discovery and communication, for relay and one-to-onecommunication (between UEs directly and between UEs over LTE-Uu).Lastly, PC6 is a reference point may be used for functions such as ProSeDiscovery between users subscribed to different PLMNs.

EPC (Evolved Packet Core) includes entities such as MME, S-GW, P-GW,PCRF, HSS etc. The EPC here represents the E-UTRAN Core Networkarchitecture. Interfaces inside the EPC may also be impacted albeit theyare not explicitly shown in FIG. 9.

Application servers, which are users of the ProSe capability forbuilding the application functionality, e.g. in the Public Safety casesthey can be specific agencies (PSAP) or in the commercial cases socialmedia. These applications are defined outside the 3GPP architecture butthere may be reference points towards 3GPP entities. The Applicationserver can communicate towards an application in the UE.

Applications in the UE use the ProSe capability for building theapplication functionality. Example may be for communication betweenmembers of Public Safety groups or for social media application thatrequests to find buddies in proximity. The ProSe Function in the network(as part of EPS) defined by 3GPP has a reference point towards the ProSeApp Server, towards the EPC and the UE.

The functionality may include but not restricted to e.g.:

-   -   Interworking via a reference point towards the 3rd party        Applications    -   Authorization and configuration of the UE for discovery and        Direct communication    -   Enable the functionality of the EPC level ProSe discovery    -   ProSe related new subscriber data and/handling of data storage;        also handling of ProSe identities;    -   Security related functionality    -   Provide Control towards the EPC for policy related functionality    -   Provide functionality for charging (via or outside of EPC, e.g.        offline charging)

Especially, the following identities are used for ProSe DirectCommunication: Source Layer-2 ID identifies a sender of a D2D packet atPC5 interface. The Source Layer-2 ID is used for identification of thereceiver RLC UM entity;

-   -   Destination Layer-2 ID identifies a target of the D2D packet at        PC5 interface. The Destination Layer-2 ID is used for filtering        of packets at the MAC layer. The Destination Layer-2 ID may be a        broadcast, groupcast or unicast identifier; and    -   SA L1 ID identifier in Scheduling Assignment (SA) at PC5        interface. SA L1 ID is used for filtering of packets at the        physical layer. The SA L1 ID may be a broadcast, groupcast or        unicast identifier.

No Access Stratum signaling is required for group formation and toconfigure Source Layer-2 ID and Destination Layer-2 ID in the UE. Thisinformation is provided by higher layers.

In case of groupcast and unicast, the MAC layer will convert the higherlayer ProSe ID (i.e. ProSe Layer-2 Group ID and ProSe UE ID) identifyingthe target (Group, UE) into two bit strings of which one can beforwarded to the physical layer and used as SA L1 ID whereas the otheris used as Destination Layer-2 ID. For broadcast, L2 indicates to L1that it is a broadcast transmission using a pre-defined SA L1 ID in thesame format as for group- and unicast.

FIG. 10 is a conceptual diagram illustrating for a Layer 2 structure forSidelink.

The Sidelink is UE to UE interface for ProSe direct communication andProSe Direct Discovery. Corresponds to the PC5 interface. The Sidelinkcomprises ProSe Direct Discovery and ProSe Direct Communication betweenUEs. The Sidelink uses uplink resources and physical channel structuresimilar to uplink transmissions. However, some changes, noted below, aremade to the physical channels. E-UTRA defines two MAC entities; one inthe UE and one in the E-UTRAN. These MAC entities handle the followingtransport channels additionally, i) sidelink broadcast channel (SL-BCH),ii) sidelink discovery channel (SL-DCH) and iii) sidelink shared channel(SL-SCH).

-   -   Basic transmission scheme: the Sidelink transmission uses the        same basic transmission scheme as the UL transmission scheme.        However, sidelink is limited to single cluster transmissions for        all the sidelink physical channels. Further, sidelink uses a 1        symbol gap at the end of each sidelink sub-frame.    -   Physical-layer processing: the Sidelink physical layer        processing of transport channels differs from UL transmission in        the following steps:

i) Scrambling: for PSDCH and PSCCH, the scrambling is not UE-specific;

ii) Modulation: 64 QAM is not supported for Sidelink.

-   -   Physical Sidelink control channel: PSCCH is mapped to the        Sidelink control resources. PSCCH indicates resource and other        transmission parameters used by a UE for PSSCH.    -   Sidelink reference signals: for PSDCH, PSCCH and PSSCH        demodulation, reference signals similar to uplink demodulation        reference signals are transmitted in the 4th symbol of the slot        in normal CP and in the 3rd symbol of the slot in extended        cyclic prefix. The Sidelink demodulation reference signals        sequence length equals the size (number of sub-carriers) of the        assigned resource. For PSDCH and PSCCH, reference signals are        created based on a fixed base sequence, cyclic shift and        orthogonal cover code.    -   Physical channel procedure: for in-coverage operation, the power        spectral density of the sidelink transmissions can be influenced        by the eNB.

FIG. 11a is a conceptual diagram illustrating for User-Plane protocolstack for ProSe Direct Communication, and FIG. 11b is Control-Planeprotocol stack for ProSe Direct Communication.

FIG. 11a shows the protocol stack for the user plane, where PDCP, RLCand MAC sublayers (terminate at the other UE) perform the functionslisted for the user plane (e.g. header compression, HARQretransmissions). The PC5 interface consists of PDCP, RLC, MAC and PHYas shown in FIG. 11 a.

User plane details of ProSe Direct Communication: i) MAC sub headercontains LCIDs (to differentiate multiple logical channels), ii) The MACheader comprises a Source Layer-2 ID and a Destination Layer-2 ID, iii)At MAC Multiplexing/demultiplexing, priority handling and padding areuseful for ProSe Direct communication, iv) RLC UM is used for ProSeDirect communication, v) Segmentation and reassembly of RLC SDUs areperformed, vi) A receiving UE needs to maintain at least one RLC UMentity per transmitting peer UE, vii) An RLC UM receiver entity does notneed to be configured prior to reception of the first RLC UM data unit,and viii) U-Mode is used for header compression in PDCP for ProSe DirectCommunication.

FIG. 11b shows the protocol stack for the control plane, where RRC, RLC,MAC, and PHY sublayers (terminate at the other UE) perform the functionslisted for the control plane. A D2D UE does not establish and maintain alogical connection to receiving D2D UEs prior to a D2D communication.

FIG. 12 is a conceptual diagram illustrating for a PC5 interface forProSe Direct Discovery.

ProSe Direct Discovery is defined as the procedure used by theProSe-enabled UE to discover other ProSe-enabled UE(s) in its proximityusing E-UTRA direct radio signals via PC5.

Radio Protocol Stack (AS) for ProSe Direct Discovery is shown in FIG.12.

The AS layer performs the following functions:

-   -   Interfaces with upper layer (ProSe Protocol): The MAC layer        receives the discovery information from the upper layer (ProSe        Protocol). The IP layer is not used for transmitting the        discovery information.    -   Scheduling: The MAC layer determines the radio resource to be        used for announcing the discovery information received from        upper layer.    -   Discovery PDU generation: The MAC layer builds the MAC PDU        carrying the discovery information and sends the MAC PDU to the        physical layer for transmission in the determined radio        resource. No MAC header is added.

There are two types of resource allocation for discovery informationannouncement.

-   -   Type 1: A resource allocation procedure where resources for        announcing of discovery information are allocated on a non UE        specific basis, further characterized by: i) The eNB provides        the UE(s) with the resource pool configuration used for        announcing of discovery information. The configuration may be        signalled in SIB, ii) The UE autonomously selects radio        resource(s) from the indicated resource pool and announce        discovery information, iii) The UE can announce discovery        information on a randomly selected discovery resource during        each discovery period.    -   Type 2: A resource allocation procedure where resources for        announcing of discovery information are allocated on a per UE        specific basis, further characterized by: i) The UE in        RRC_CONNECTED may request resource(s) for announcing of        discovery information from the eNB via RRC, ii) The eNB assigns        resource(s) via RRC, iii) The resources are allocated within the        resource pool that is configured in UEs for monitoring.

For UEs in RRC_IDLE, the eNB may select one of the following options:

-   -   The eNB may provide a Type 1 resource pool for discovery        information announcement in SIB. UEs that are authorized for        Prose Direct Discovery use these resources for announcing        discovery information in RRC_IDLE.    -   The eNB may indicate in SIB that it supports D2D but does not        provide resources for discovery information announcement. UEs        need to enter RRC Connected in order to request D2D resources        for discovery information announcement.

For UEs in RRC_CONNECTED,

-   -   A UE authorized to perform ProSe Direct Discovery announcement        indicates to the eNB that it wants to perform D2D discovery        announcement.    -   The eNB validates whether the UE is authorized for ProSe Direct        Discovery announcement using the UE context received from MME.    -   The eNB may configure the UE to use a Type 1 resource pool or        dedicated Type 2 resources for discovery information        announcement via dedicated RRC signaling (or no resource).    -   The resources allocated by the eNB are valid until a) the eNB        de-configures the resource(s) by RRC signaling or b) the UE        enters IDLE. (FFS whether resources may remain valid even in        IDLE).

Receiving UEs in RRC_IDLE and RRC_CONNECTED monitor both Type 1 and Type2 discovery resource pools as authorized. The eNB provides the resourcepool configuration used for discovery information monitoring in SIB. TheSIB may contain discovery resources used for announcing in neighborcells as well.

FIG. 13 is a conceptual diagram illustrating for overview model of theRLC sub layer.

Functions of the RLC sub layer are performed by RLC entities. For a RLCentity configured at the eNB, there is a peer RLC entity configured atthe UE and vice versa. For an RLC entity configured at the transmittingUE for STCH or SBCCH there is a peer RLC entity configured at eachreceiving UE for STCH or SBCCH.

An RLC entity receives/delivers RLC SDUs from/to upper layer andsends/receives RLC PDUs to/from its peer RLC entity via lower layers. AnRLC PDU can either be a RLC data PDU or a RLC control PDU. If an RLCentity receives RLC SDUs from upper layer, it receives them through asingle SAP between RLC and upper layer, and after forming RLC data PDUsfrom the received RLC SDUs, the RLC entity delivers the RLC data PDUs tolower layer through a single logical channel. If an RLC entity receivesRLC data PDUs from lower layer, it receives them through a singlelogical channel, and after forming RLC SDUs from the received RLC dataPDUs, the RLC entity delivers the RLC SDUs to upper layer through asingle SAP between RLC and upper layer. If an RLC entitydelivers/receives RLC control PDUs to/from lower layer, itdelivers/receives them through the same logical channel itdelivers/receives the RLC data PDUs through.

An RLC entity can be configured to perform data transfer in one of thefollowing three modes: Transparent Mode (TM), Unacknowledged Mode (UM)or Acknowledged Mode (AM). Consequently, an RLC entity is categorized asa TM RLC entity, an UM RLC entity or an AM RLC entity depending on themode of data transfer that the RLC entity is configured to provide.

A TM RLC entity is configured either as a transmitting TM RLC entity ora receiving TM RLC entity. The transmitting TM RLC entity receives RLCSDUs from upper layer and sends RLC PDUs to its peer receiving TM RLCentity via lower layers. The receiving TM RLC entity delivers RLC SDUsto upper layer and receives RLC PDUs from its peer transmitting TM RLCentity via lower layers.

An UM RLC entity is configured either as a transmitting UM RLC entity ora receiving UM RLC entity. The transmitting UM RLC entity receives RLCSDUs from upper layer and sends RLC PDUs to its peer receiving UM RLCentity via lower layers. The receiving UM RLC entity delivers RLC SDUsto upper layer and receives RLC PDUs from its peer transmitting UM RLCentity via lower layers.

An AM RLC entity consists of a transmitting side and a receiving side.The transmitting side of an AM RLC entity receives RLC SDUs from upperlayer and sends RLC PDUs to its peer AM RLC entity via lower layers. Thereceiving side of an AM RLC entity delivers RLC SDUs to upper layer andreceives RLC PDUs from its peer AM RLC entity via lower layers.

The following applies to all RLC entity types (i.e. TM, UM and AM RLCentity): i) RLC SDUs of variable sizes which are byte aligned (i.e.multiple of 8 bits) are supported, and ii) RLC PDUs are formed only whena transmission opportunity has been notified by lower layer (i.e. byMAC) and are then delivered to lower layer.

FIG. 14 is a conceptual diagram illustrating for model of twounacknowledged mode peer entities.

In UM (Unacknowledged Mode), in-sequence delivery to higher layers isprovided, but no retransmissions of missing PDUs are requested. UM istypically used for services such as VoIP where error-free delivery is ofless importance compared to short delivery time. TM (Transparent Mode),although supported, is only used for specific purposes such as randomaccess.

Unacknowledged mode (UM) supports segmentation/reassembly andin-sequence delivery, but not retransmissions. This mode is used whenerror-free delivery is not required, for example voice-over IP, or whenretransmissions cannot be requested, for example broadcast transmissionson MTCH and MCCH using MBSFN.

When a transmitting UM RLC entity forms UMD PDUs from RLC SDUs, thetransmitting UM RLC entity may i) segment and/or concatenate the RLCSDUs so that the UMD PDUs fit within the total size of RLC PDU(s)indicated by lower layer at the particular transmission opportunitynotified by lower layer; and ii) include relevant RLC headers in the UMDPDU.

When a receiving UM RLC entity receives UMD PDUs, the receiving UM RLCentity may i) detect whether or not the UMD PDUs have been received induplication, and discard duplicated UMD PDUs; ii) reorder the UMD PDUsif they are received out of sequence; iii) detect the loss of UMD PDUsat lower layers and avoid excessive reordering delays; iv) reassembleRLC SDUs from the reordered UMD PDUs (not accounting for RLC PDUs forwhich losses have been detected) and deliver the RLC SDUs to upper layerin ascending order of the RLC SN; and v) discard received UMD PDUs thatcannot be reassembled into a RLC SDU due to loss at lower layers of anUMD PDU which belonged to the particular RLC SDU.

At the time of RLC re-establishment, the receiving UM RLC entity mayreassemble RLC SDUs from the UMD PDUs that are received out of sequenceand deliver them to upper layer, if possible; ii) discard any remainingUMD PDUs that could not be reassembled into RLC SDUs; and iii)initialize relevant state variables and stop relevant timers.

FIG. 15 is a conceptual diagram for functional view of a PDCP entity.

The PDCP entities are located in the PDCP sublayer. Several PDCPentities may be defined for a UE. Each PDCP entity carrying user planedata may be configured to use header compression. Each PDCP entity iscarrying the data of one radio bearer. In this version of thespecification, only the robust header compression protocol (ROHC), issupported. Every PDCP entity uses at most one ROHC compressor instanceand at most one ROHC decompressor instance. A PDCP entity is associatedeither to the control plane or the user plane depending on which radiobearer it is carrying data for.

FIG. 15 represents the functional view of the PDCP entity for the PDCPsublayer, it should not restrict implementation. For RNs, integrityprotection and verification are also performed for the u-plane.

UL Data Transfer Procedures:

At reception of a PDCP SDU from upper layers, the UE may start a discardtimer associated with the PDCP SDU. For a PDCP SDU received from upperlayers, the UE may associate a PDCP SN (Sequence Number) correspondingto Next_PDCP_TX_SN to the PDCP SDU, perform header compression of thePDCP SDU, perform integrity protection and ciphering using COUNT basedon TX_HFN and the PDCP SN associated with this PDCP SDU, increment theNext_PDCP_TX_SN by one, and submit the resulting PDCP Data PDU to lowerlayer.

If the Next_PDCP_TX_SN is greater than Maximum_PDCP_SN, theNext_PDCP_TX_SN is set to ‘0’ and TX_HFN is incremented by one.

DL Data Transfer Procedures:

For DRBs mapped on RLC UM, at reception of a PDCP Data PDU from lowerlayers, if received PDCP SN<Next_PDCP_RX_SN, the UE may increment RX_HFNby one, and decipher the PDCP Data PDU using COUNT based on RX_HFN andthe received PDCP SN. And the UE may set Next_PDCP_RX_SN to the receivedPDCP SN+1. If Next_PDCP_RX_SN>Maximum_PDCP_SN, the UE may setNext_PDCP_RX_SN to 0, and increment RX_HFN by one.

The UE may perform header decompression (if configured) of thedeciphered PDCP Data PDU, and deliver the resulting PDCP SDU to upperlayer.

FIG. 16 is a conceptual diagram for transmitting aRadioResourceConfigDedicated from E-UTRAN to a UE.

The UE may establish a PDCP entity and configure it with the currentsecurity configuration and in accordance with the received pdcp-Configand establish an RLC entity or entities in accordance with the receivedrlc-Config, for each drb-Identity value included in the drb-ToAddModListthat is not part of the current UE configuration.

The IE RadioResourceConfigDedicated is used to setup/modify/release RBs,to modify the MAC main configuration, to modify the SPS configurationand to modify dedicated physical configuration.

The IE RadioResourceConfigDedicated includes the drb-ToAddModListincluding pdcp-Config and rlc-Config, such as following Table 1.

TABLE 1 RadioResourceConfigDedicated information element -- ASN1STARTRadioResourceConfigDedicated : := SEQUENCE { srb-ToAddModListSRB-ToAddModList OPTIONAL, -- Cond HO-Conn drb-ToAddModListDRB-ToAddModList OPTIONAL, -- Cond HO- .... SRB-ToAddModList : :=SEQUENCE (SIZE (1..2)) OF SRB-ToAddMod SRB-ToAddMod : := SEQUENCE {srb-Identity INTEGER (1..2), -- Cond Setup rlc-Config CHOICE {explicitValue RLC-Config, defaultValue NULL } OPTIONALlogicalChannelConfigOPTIONAL, CHOICE { -- Cond Setup explicitValueLogicalChannelConfig, defaultValue NULL } OPTIONAL ... }DRB-ToAddModList : := SEQUENCE (SIZE (1..maxDRB)) OF DRB-ToAddModDRB-ToAddMod = SEQUENCE { eps-Bearer Identity INTEGER (0..15) OPTIONAL,-- Cond DRB-Setup drb-Identity DRB-Identity, pdcp-Config PDCP-ConfigOPTIONAL, -- Cond DRB-Setup rlc-Config RLC-Config OPTIONAL, -- CondSetup logical Channel Identity INTEGER (3..10) OPTIONAL, -- CondDRB-Setup logical ChannelConfig Logical Channel Config OPTIONAL, -- CondSetup .... }

The IE RLC-Config is used to specify the RLC configuration of SRBs andDRBs.

For SRBs a choice is used to indicate whether the RLC configuration issignaled explicitly or set to the values defined in the default RLCconfiguration for SRB1 or for SRB2. RLC AM is the only applicable RLCmode for SRB1 and SRB2. E-UTRAN does not reconfigure the RLC mode ofDRBs except when a full configuration option is used, and mayreconfigure the UM RLC SN field size only upon handover within E-UTRA orupon the first reconfiguration after RRC connection re-establishment.

The RLC-Config includes parameters of SN-FieldLength and T-Reordering,and so on.

The SN-FieldLength Indicates the UM RLC SN field size in bits. Valuesize5 means 5 bits, size10 means 10 bits.

The T-Reordering is a timer for reordering in milliseconds. Value ms0means 0 ms, ms5 means 5 ms and so on

TABLE 2 RLC-config information element -- ASN1START RLC-Config ::=CHOICE { SEQUENCE { am ul-AM-RLC UL-AM-RLC dl-AM-RLC DL-AM-RLC },um-Bi-Directional SEQUENCE { ul-UM-RLC UL-UM-RLC dl-UM-RLC DL-UM-RLC },um-Uni-Directional-UL SEQUENCE { ul-UM-RLC UL-UM-RLC },um-Uni-Directional-UL SEQUENCE { dl-UM-RLC DL-UM-RLC }, ... ....SN-FieldLength : := ENUMERATED {size5, size10} T-Pol IRetransmit : :=ENUMERATED { ms5, ms10, ms15, ms20, ms 25, ms30, ms35, ms40, ms45, ms50,ms55, ms00, ms65, ms70, ms75, ms80, ms85, ms90, ms95, ms100, ms105,ms110, ms115, ms120, ms125, ms130, ms135, ms140, ms145, ms150, ms155,ms150, ms155, ms170, ms175, ms180, ms185, ms190, ms195, ms200, ms205,ms210, ms215, ms220, ms225 ms230, ms235, ms240, ms245, ms250, ms350,ms400, ms450, ms500, spare9, spare8, spare7, spare6, spare5, spare4,spare3, spare2, spare1} ENUMERATED { Pol I PDU : := P4, p8, P16, p32,p64, p128, p256, pInfinity} Pol I Byte : := ENUMERATED { kB25, kB50,kB75, kB100, kB125, kB250, kB375, kB500, kB750, kB1000, kB1250, kB1500,kB2000, kB3000, kBinfinity, spareI} T-Reordering : := ENUMERATED { ms0,ms5, ms10, ms15, ms20, ms25, ms30, ms35, ms40, ms45, ms 50, ms 55, ms80,ms65, ms 70, ms 75, ms80, 5505, ms90, ms95, ms100, ms110, ms120, ms130,ms140, ms150, ms160, ms170, ms180, ms190, ms200, spare1}

The IE PDCP-Config is used to set the configurable PDCP parameters fordata radio bearers.

The PDCP-Config includes parameters of pdcp-SN-size andheaderCompression.

The pdcp-SN-size indicates the PDCP Sequence Number length in bits. ForRLC UM: value len7bits means that the 7-bit PDCP SN format is used andlen12bits means that the 12-bit PDCP SN format is used. For RLC AM:value len15bits means that the 15-bit PDCP SN format is used, otherwiseif the field is not included upon setup of the PCDP entity 12-bit PDCPSN format is used

PDCP-config information element -- ASN1START PDCP-Config ::= SEQUENCE {discardTimer ENUMERATED { ms50, ms100, ms150, ms300, ms500, ms750,ms1500, Infinity OPTIONAL, -- Cond Setup } SEQUENCE { rlc-AM BOOLEANstatusReportRequired OPTIONAL, -- Cond Rlc-AM } SEQUENCE { rlc-UMENUMERATED {len7bits, len12bits} pdcp-SN-Size OPTIONAL, -- Cond Rlc-UM }headerCompression CHOICE { notUsed NULL, rohc SEQUENCE { maxCID INTEGER(1..16383) DEFAULT 15, profiles SEQUENCE { profile0x0001 BOOLEAN,profile0x0002 BOOLEAN, profile0x0003 BOOLEAN, profile0x0004 BOOLEAN,profile0x0006 BOOLEAN, profile0x0101 BOOLEAN, profile0x0102 BOOLEAN,profile0x0103 BOOLEAN, profile0x0104 BOOLEAN, }, ENUMERATED {enabled}OPTIONAL -- Cond RN ... ENUMERATED i{en15bits} OPTIONAL -- Cond Rlc-AM2} BOOLEAN OPTIONAL, -- Need ON }, ENUMERATED { ..., ms0, ms20, ms40,ms60, ms80, ms100, ms120, ms140, [[ rn-IntegrityProtection-r10 ms160,ms180, ms200, ms220, ms240, ms260, ms280, ]], ms300, ms500, ms750,spareI4, spareI3, spareI2, spareI1, [[ pdcp-SN-Size-v1130 spare10,spare9, spare8, spare7, spare6, spare5, spare4, ]], spare3, spare2,spare1} [[ ul-DataSplitDRB-ViaSCG-r12t- OPTIONAL -- Cond SetupSReordering-r12 ]] } -- ASN1STOP

The maxCID indicates the value of the MAX_CID parameter. The total valueof MAX_CIDs across all bearers for the UE should be less than or equalto the value of maxNumberROHC-ContextSessions parameter as indicated bythe UE, and the profiles used by both compressor and decompressor inboth UE and E-UTRAN. The field indicates which of the ROHC profiles aresupported, i.e. value true indicates that the profile is supported.Profile 0x0000 shall always be supported when the use of ROHC isconfigured. If support of two ROHC profile identifiers with the same 8LSB's is signaled, only the profile corresponding to the highest valueshall be applied.

In the legacy system, a UE establishes L2 entities such as a PDCP entityand an RLC entity in accordance with the RRC message (i.e., rlc-Configand pdcp-Config) when a radio bearer is added by an eNB. The RRC messagefor L2 entity configuration includes parameters and timer informationaccording to its mode (AM, UM, TM).

In D2D communication, RLC UM mode is only applicable for D2D radiobearer. The receiving UE (rxUE) maintains at least one RLC entity pertransmitting UE (txUE). However, the RLC entity in UE-RX does not needto be configured prior to reception of the first RLC UM data unit. Themotivation is not to maintain a L2 entity (RLC or PDCP entities) unlessthere is D2D communication. Accordingly, the L2 entity will beestablished upon receiving the very first D2D data and released whenthere is no D2D communication.

In order to establish L2 entities, a UE should have proper configurationinformation to be applied to each RLC and PDCP entity. Given that D2Dcommunication is performed using PC5 interface between txUE and rxUE,the conventional mechanism that eNB provides L2 entity configurationinformation to the rxUE cannot be applied to D2D communication.

FIG. 17 is a conceptual diagram for establishing layer-2 entities forD2D communication according to embodiments of the present invention.

In D2D communication, for the receiving UE (rxUE) to establish layer2entities such as PDCP entity and RLC entity for a sidelink radio bearer,it is invented that the txUE transmits layer2 entity configurationinformation (D2D-L2ConfigInfo) to the rxUE at D2D radio bearer setup,and rxUE establishes layer2 entities for the D2D radio bearer based onthe D2D-L2ConfigInfo received from the txUE.

When a transmitting UE configures a sidelink radio bearer over which thetransmitting UE transmits data to a receiving UE (S1701), thetransmitting UE establishes RLC and PDCP entities for the sidelink radiobearer by setting PDCP-SN-Size, headerCompression, SN-FieldLength, andT-Reordering by taking QoS of the sidelink into account (S1703).

The transmitting UE transmits configuration information of the sidelinkradio bearer via a sidelink to the receiving UE (S1705).

Preferably, the transmitting UE is directly connected to the receivingUE via the sidelink.

Preferably, the configuration information is transmitted via a first D2Dpacket, wherein the first D2D packet is transmitted before transmittingany other D2D packets of the sidelink radio bearer to the receiving UE.

Preferably, the first D2D packet further includes at least one of atarget ID, a source ID or LCID. The receiving UE is identified bytargetID, the transmitting UE is identified by sourceID, and a logicalchannel of the sidelink radio bearer is identified by the LCID.

Preferably, the configuration information includes at least one of thefollowing: PDCP-SN-Size, a headerCompression, or a SN-FieldLength andT-Reordering. Especially, the T-Reordering is a parameter used for anRLC entity for the receiving UE.

Preferably, the configuration information is transmitted one or multipletimes to the peer UE, wherein the transmission number of configurationinformation is configured by the network or pre-defined.

Preferably, the configuration information is transmitted periodically tothe peer UE, wherein periodicity of transmitting configurationinformation is configured by the network or pre-defined.

Preferably, the configuration information is transmitted as form of atleast one of RRC (Radio Resource Control), PDCP (Packet Data ConvergenceProtocol), RLC (Radio Link Control), MAC (Medium Access Control), or PHY(PHYsical) signal.

When the receiving UE receives the configuration information of thesidelink radio bearer via a sidelink from the transmitting UE (S1705),the receiving UE configures the sidelink radio bearer according to theconfiguration information (S1707) and establishes RLC and PDCP entitiesfor the sidelink radio bearer if the RLC and PDCP entities are notestablished yet (S1709).

The receiving UE establishes the PDCP entity and the RLC entity for thesidelink radio bearer associated with the received targetID, sourceID,and LCID by setting PDCP-SN-Size, headerCompression, SN-FieldLength, andT-Reordering to the values received in the configuration information.

After the step of S1709, the receiving UE the configuration informationto the established RLC and PDCP entities (S1711).

If the RLC and PDCP entities are already established for the sidelinkradio bearer associated with the received the target ID, source ID andLCID, the receiving UE can ignore the received configurationinformation, or the receiving UE can update the RLC and PDCP entitiesfor the sidelink associated with a targetID, a sourceID, and a LCID bysetting the PDCP-SN-Size, the headerCompression, the SN-FieldLength, andthe T-Reordering to the values received in the configurationinformation.

FIG. 18 is a conceptual diagram for establishing layer-2 entities forD2D communication according to embodiments of the present invention.

When a transmitting UE configures a sidelink radio bearer over which thetransmitting UE transmits data to a receiving UE (S1801), thetransmitting UE establishes RLC and PDCP entities for the sidelink radiobearer for the sidelink radio bearer by selecting one of configurationinformation sets (S1803).

Preferably, the configuration information sets are pre-defined for thesidelink radio bearer.

Preferably, the configuration information set includes at least one ofparameters including a PDCP-SN-Size, a headerCompression, aSN-FieldLength and a T-Reordering.

For example, D2D-L2ConfigInfo set #1 is [PDCP-SN-Size=5 bit,headerCompression=ON, SN-FieldLength=7 bit, T-Reordering=10 ms]; andD2D-L2ConfigInfo set #2 is [PDCP-SN-Size=5 bit, headerCompression=01-1-,SN-FieldLength=7 bit, T-Reordering=30 ms].

Thus, the transmitting UE sets PDCP-SN-Size, headerCompression,SN-FieldLength, and T-Reordering for the sidelink radio bearer to thevalues of the selected configuration information set.

Preferably, each configuration information set is identified by eachconfiguration information index. The configuration information index canbe associated with an ID (e.g., LCID). The LCID is an identifier of alogical channel of the sidelink radio bearer.

One configuration information index may indicate one configurationinformation set. And multiple configuration information indices can beassociated with one configuration information set. For example,configuration information indices 1˜10 is associated withD2D-L2ConfigInfo set #1, configuration information indices 11˜20 isassociated with D2D-L2ConfigInfo set #2.

Preferably, the transmitting UE can configure mapping relation betweenconfiguration information sets and indices and transmit the mappingrelation to the receiving UE. Alternatively, the transmitting UE canreceive mapping relation between configuration information sets andindices from a network. Accordingly, the transmitting UE and thereceiving UE acquire same information on the mapping relation betweenconfiguration information sets and indices.

The transmitting UE transmits the first D2D packet of the sidelink radiobearer including at least one of the followings: i) an index of theselected configuration information set ii) a targetID identifying thereceiving UE, and iii) a sourceID identifying the transmitting UE, andiv) a LCID identifying a logical channel of the sidelink radio bearer(S1805).

Preferably, the first D2D packet is transmitted via a sidelink to thepeer UE, wherein the UE is directly connected to the peer UE via thesidelink.

Preferably, the first D2D packet is transmitted before transmitting anyother D2D packets of the sidelink radio bearer to the receiving UE.

Preferably, the LCID can be used for the index of the selectedconfiguration information set. In this case, if LCID is used for theindex of the selected configuration information set, the first D2Dpacket may not include the index of the selected configurationinformation set.

Preferably, the index of the selected configuration information set istransmitted one or multiple times to the peer UE, wherein thetransmission number of the index is configured by the network orpre-defined.

Preferably, the index of the selected configuration information set istransmitted periodically to the peer UE, wherein periodicity oftransmitting the index is configured by the network or pre-defined.

Preferably, the index of the selected configuration information set istransmitted as form of at least one of RRC (Radio Resource Control),PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC(Medium Access Control), or PHY (PHYsical layer) signal.

When the receiving UE receives the index of a sidelink radio bearer viaa sidelink from the transmitting UE (S1805), the receiving UE configuresthe sidelink radio bearer according to the configuration information setindicated by the index (S1807).

Preferably, the index can be received via the first D2D packet includingthe target ID, the sourceID and the LCID. If a PDCP entity and a RLCentity are not established yet for the sidelink radio bearer associatedwith the received targetID, sourceID, and LCID, the receiving UE setupsthe sidelink radio bearer associated with the received targetID,sourceID, and LCID (S1809). I.e., the receiving UE establishes the PDCPentity and the RLC entity for the sidelink radio bearer associated withthe received targetID, sourceID, and LCID by setting PDCP-SN-Size,headerCompression, SN-FieldLength, and T-Reordering to the values inconfiguration information set indicated by the index.

And the receiving UE delivers the first D2D packet including the indexto the established RLC and PDCP entities (S1811).

If PDCP entity and RLC entity are already established for the sidelinkradio bearer associated with the received targetID, sourceID, and LCID,the receiving UE does not change the layer2 configuration parameters forthe PDCP entity and the RLC entity associated with the index of thereceived D2D packet.

Alternately, if PDCP entity and RLC entity are already established forthe sidelink radio bearer associated with the received targetID,sourceID, and LCID, the receiving UE updates the PDCP entity and the RLCentity for the sidelink radio bearer associated with the receivedtargetID, sourceID, and LCID by setting PDCP-SN-Size, headerCompression,SN-FieldLength, and T-Reordering to the values in configurationinformation set indicated by the ID. And then, the receiving UE deliversthe first D2D packet including the index to the established RLC and PDCPentities associated with [targetID, sourceID, LCID].

FIG. 19 is an examplary diagram for establishing layer-2 entities forD2D communication according to embodiments of the present invention.

The network informs the txUE and the rxUE of information onD2D-L2ConfigInfo set and associated LCIDs (S1901).

The txUE with sourceID=12 setups SIDELINK RADIO BEARER #1 usingD2D-L2ConfigInfo set #1. For that SIDELINK RADIO BEARER #1, the txUEselects LCID=00011 as a D2D-L2ConfigInfo-Id. The txUE with sourceID=9setups SIDELINK RADIO BEARER #2 using D2D-L2ConfigInfo set #2. For thatSIDELINK RADIO BEARER #2, the txUE selects LCID=01001 as aD2D-L2ConfigInfo-Id.

The txUE with sourceID=12 transmits the D2D packet of that SIDELINKRADIO BEARER #1 to the rxUE by including LCID=00011 in the D2D packet,e.g., MAC PDU (S1903).

When the rxUE receives a D2D packet of SIDELINK RADIO BEARER #1, therxUE checks whether PDCP and RLC entities are already established forthe SIDELINK RADIO BEARER associated with [targetID=47, sourceID=12,LCID=00011]. If there is no PDCP and RLC entities for the SIDELINK RADIOBEARER associated with [targetID=47, sourceID=12, LCID=00011], the rxUEestablishes PDCP and RLC entities by setting the layer2 entityconfiguration parameters to the values of D2D-L2ConfigInfo set indicatedby the LCID. In this example, since LCID=00011 indicatesD2D-L2ConfigInfo set #1, the UE establishes the PDCP entity and the RLCentity for that SIDELINK RADIO BEARER #1 by setting PDCP-SN-Size=7 bit,headerCompression=ON, SN-FieldLength=5 bit, and T-Reordering=10 ms.

The rxUE delivers the D2D packet of SIDELINK RADIO BEARER #1 to the RLCand PDCP entity associated with [targetID=47, sourceID=12, LCID=00011].

The txUE with sourceID=9 transmits the D2D packet of that SIDELINK RADIOBEARER #2 to the rxUE by including LCID=01001 in the D2D packet, e.g.,MAC PDU (S1905).

When the rxUE receives a D2D packet of SIDELINK RADIO BEARER #2, therxUE checks whether PDCP and RLC entities are already established forthe SIDELINK RADIO BEARER associated with [targetID=47, sourceID=9,LCID=01001]. If there is no PDCP and RLC entities for the SIDELINK RADIOBEARER associated with [targetID=47, sourceID=9, LCID=01001], the rxUEestablishes PDCP and RLC entities by setting the layer2 entityconfiguration parameters to the values of D2D-L2ConfigInfo set indicatedby the LCID. In this example, since LCID=01001 indicatesD2D-L2ConfigInfo set #2, the UE establishes the PDCP entity and the RLCentity for that SIDELINK RADIO BEARER #2 by setting PDCP-SN-Size=12 bit,headerCompression=OFF, SN-FieldLength=10 bit, and T-Reordering=100 ms.

The rxUE delivers the D2D packet of SIDELINK RADIO BEARER #2 to the RLCand PDCP entity associated with [targetID=47, sourceID=9, LCID=01001].

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

1. A method for a User Equipment (UE) operating in a wirelesscommunication system, the method comprising: configuring a sidelinkradio bearer over which the UE transmits data to a peer UE; establishingRadio Link Control (RLC) and Packet Data Convergence Protocol (PDCP)entities for the sidelink radio bearer by selecting one of configurationinformation sets, wherein each configuration information set isidentified by each configuration information index; and transmitting anindex of the selected configuration information set via a sidelink tothe peer UE, wherein the UE is directly connected to the peer UE via thesidelink.
 2. The method according to claim 1, further comprising:configuring, by the UE, a mapping relation between configurationinformation sets and indices; and transmitting the mapping relation tothe peer UE.
 3. The method according to claim 1, further comprising:receiving, by the UE, a mapping relation between configurationinformation sets and indices from a network.
 4. The method according toclaim 1, wherein a logical channel identifier (LCID) is used for theconfiguration information index, wherein the LCID is an identifier of alogical channel of the sidelink radio bearer.
 5. The method according toclaim 1, wherein the index of the selected configuration information setis transmitted one or multiple times to the peer UE, wherein atransmission number of the index is configured by the network orpredefined.
 6. The method according to claim 1, wherein the index of theselected configuration information set is transmitted periodically tothe peer UE, wherein periodicity of transmitting the index is configuredby the network or predefined.
 7. (canceled)
 8. The method according toclaim 1, wherein the index of the selected configuration information setis transmitted via a first Device to Device (D2D) packet, wherein thefirst D2D packet is transmitted before transmitting any other D2Dpackets of the sidelink radio bearer to the peer UE.
 9. The methodaccording to claim 8, wherein the first D2D packet further includes atleast one of a target identifier (ID) MDR a source ID or a logicalchannel identifier (LCID).
 10. A method for a User Equipment (UE)operating in a wireless communication system, the method comprising:receiving an index of a configuration information set via a sidelinkfrom the peer UE, wherein the UE is directly connected to the peer UEvia the sidelink and, wherein the configuration information setcorresponds to a sidelink radio bearer to be configured; configuring thesidelink radio bearer according to the configuration information setindicated by the index; and establishing Radio Link Control (RLC) andPacket Data Convergence Protocol (PDCP) entities for the sidelink radiobearer if the RLC and PDCP entities are not established yet.
 11. Themethod according to claim 10, further comprising: receiving, by the UE,a mapping relation between configuration information sets and indicesfrom the peer UE or a network.
 12. The method according to claim 10,wherein a logical channel identifier (LCID) is used for theconfiguration information index, wherein the LCID is an identifier of alogical channel of the sidelink radio bearer.
 13. The method accordingto claim 10, wherein one or more LCIDs are associated with oneconfiguration information set.
 14. The method according to claim 10,wherein each configuration information set includes at least one ofparameters including a PDCP-SN-Size, a headerCompression, aSN-FieldLength and a T-Reordering.
 15. The method according to claim 10,wherein the index of the configuration information set is received via afirst Device to Device (D2D) packet, wherein the first D2D packet isreceived before receiving any other D2D packets of the sidelink radiobearer from the peer UE.
 16. The method according to claim 15, whereinthe first D2D packet further includes at least one of a targetidentifier (ID) MDR a source ID or a logical channel identifier (LCID).17. The method according to claim 10, further comprising: deliveringwherein the index of the configuration information set to theestablished RLC and PDCP entities.
 18. The method according to claim 10,further comprising: ignoring the received the index of the configurationinformation set if the RLC and PDCP entities are already established.19. The method according to claim 14, further comprising: updating theRLC and PDCP entities for the sidelink radio bearer, when values of thePDCP-SN-Size, the headerCompression, the SN-FieldLength, and theT-Reordering are set to values in the configuration information setindicated by the index.
 20. (canceled)
 21. A user equipment (UE)operating in a wireless communication system, the UE comprising: a RadioFrequency (RF) module; and a processor operably coupled with the RFmodule and configured to: configure a sidelink radio bearer over whichthe UE transmits data to a peer UE, establish Radio Link Control (RLC)and Packet Data Convergence Protocol (PDCP) entities for the sidelinkradio bearer by selecting one of configuration information sets, whereineach configuration information set is identified by each configurationinformation index, and transmit an index of the selected configurationinformation set via a sidelink to the peer UE, wherein the UE isdirectly connected to the peer UE via the sidelink.
 22. A user equipment(UE) operating in a wireless communication system, the UE comprising: aRadio Frequency (RF) module; and a processor operably coupled with theRF module and configured to: receive an index of a configurationinformation set via a sidelink from the peer UE, wherein the UE isdirectly connected to the peer UE via the sidelink and, wherein theconfiguration information set corresponds to a sidelink radio bearer tobe configured, configure the sidelink radio bearer according to theconfiguration information set indicated by the index, and establishRadio Link Control (RLC) and Packet Data Convergence Protocol (PDCP)entities for the sidelink radio bearer if the RLC and PDCP entities arenot established yet.